Medicaid Access Increases Use of Care, Study Finds

WASHINGTON — Come January, millions of low-income adults will gain health insurance coverage through Medicaid in one of the farthest-reaching provisions of the Obama health care law. How will that change their finances, spending habits, use of available medical services and — most important — their health?

New results from a landmark study, released on Wednesday in The New England Journal of Medicine, go a long way toward answering those questions. The study, called the Oregon Health Study, compares thousands of low-income people in Oregon who received access to Medicaid with an identical population that did not.

It found that those who gained Medicaid coverage spent more on health care, making more visits to doctors and trips to the hospital. But the study suggests that Medicaid coverage did not make those adults much healthier, at least within the two-year time frame of the research, judging by their blood pressure, blood sugar and other measures. It did, however, substantially reduce the incidence of depression, and it made them vastly more financially secure.

“There was this view that Medicaid coverage would not do much for the low-income uninsured, either because they had access to charity care or because Medicaid is not good insurance,” said Amy Finkelstein of the Massachusetts Institute of Technology. “This rejects that notion entirely.” Her work on the Oregon study contributed to her receipt last year of the John Bates Clark Medal, a laurel for younger economists considered second only to the Nobel Memorial Prize in Economic Science for those in the profession.

Currently about 50 million Americans, nearly all them poor, receive health care coverage under Medicaid, a federal program administered by the states. But most states do not provide Medicaid coverage to adults without disabilities or dependent children, no matter how poor they are.

Health economists anticipate that new enrollees to the Medicaid program will swell the country’s health spending costs by hundreds of billions of dollars over time. In 2014, at least 18 states and the District of Columbia will provide coverage to all adults with incomes below 133 percent of the federal poverty line. That currently would translate to coverage for all individuals with incomes below about $15,000 and for households of four people receiving less than about $31,000.

Many more states might join in the expansion in the coming months or years. The Affordable Care Act, President Obama’s health care law, has the federal government pay for a large majority of the increased Medicaid costs in perpetuity, making the financial burden on states much smaller.

The unique Oregon study came about when the state found itself with enough money to provide additional Medicaid coverage to about 10,000 low-income adults. Many times that number qualified.

Rather than deny coverage to all Oregonians, the state established a lottery, to distribute coverage randomly. That gave economists and other social scientists a once-in-a-lifetime chance to perform a randomized control experiment — the gold standard in medical and scientific research, but a rarity in much of social science — isolating the effect that coverage had on health and broader well-being.

An earlier round of results from the Oregon Health Study analyzed assessments of health and well-being reported by study participants, as well as data from hospitals and credit agencies. This second major set of results stems from biometric data collected at in-person visits with participants. A huge team of researchers collected blood samples, blood pressure readings and weight measurements from thousands of Oregonians; about half of them had won access to Medicaid in a lottery and half had not.

The researchers found that Medicaid coverage did not significantly affect the prevalence or diagnosis of hypertension or high cholesterol, or the use of drugs used to treat those conditions. It significantly increased the probability that a person would receive a diagnosis of diabetes and be treated, though it did not reduce blood sugar levels noticeably.

Where Medicaid seemed to have the strongest measured impact was on depression. Getting Medicaid coverage reduced the probability of a positive screening by more than 30 percent.

“The authors are almost tilting the spin on the story to be a little more pessimistic than I would have been,” said John Holahan of the Urban Institute, responding to the new findings.

“There are some positive effects on health,” he said, calling the effect on depression “especially strong.”

Confirming previous findings released by the researchers, the new round of results found that adults covered by Medicaid increased their use of a broad number of health services, like mammograms and cholesterol tests. That increased their medical spending by about 35 percent, compared to adults who did not win Medicaid coverage in the lottery.

Some researchers had theorized that getting Medicaid coverage would lead to a spike in use of medical services by low-income adults. Once covered, they might visit the doctor, have conditions checked out and treated, then stop using medical services as much.

But the second set of results from the Oregon study shows that is not the case. There is no spike in use of health services, nor is there any decline later on. Rather, use of the health system increased, and that increase persisted between the first year and the second year of the study.

“They go to the doctor more often, they visit the hospital more often, they use more prescription drugs, they are more likely to use preventive care,” said Katherine Baicker, a Harvard professor, co-author of the study and former economic adviser to President George W. Bush. “There is no evidence of a spike of utilization from pent-up demand.”

A version of this article appears in print on , on Page B1 of the New York edition with the headline: Expanded Medicaid Raises Use of Care. Order Reprints | Today’s Paper | Subscribe